You know that it has happened to you before. You know when you're sitting in a room full of strangers, or even worse family and friends, and your cock decides that its hot and horny and ready to pop up in the most uncomfortable and unlikely situations. First of all, you should know that sexual thoughts and hot babes aren't the only things that can make you aroused. You can end up with an erection anytime if blood decides to flow to that area. It's like Murphy's Law; it's likely to happen when you most definitely don't want it to. Unfortunately, that truly sucks (pun not intended) but there are several ways for you to hide that erection until you can get to have a (really, extremely) cold shower or alternatively relieve your load.
Untuck! Untuck your shirt pronto! Long shirts can be your saviour in such situations. However, randomly ripping your shirt fiercely out of your trousers so you can untuck it may not only look extremely weird, but it can also bring unwanted attention to your erection, so perform this move subtly.
Cockblocking this doesn't always have to be a bad word. Use whatever you can to naturally cover up, and by naturally, this means using a book, newspaper or something non conspicuous to cover yourself up. Grabbing a random television or picture frame off the wall is again, going to bring unwanted attention to the region that you're trying to cover up. Think of everyday objects that you would, or could, naturally hold down there such as menus, or a shopping bag.
Create a distraction. At the end of the day, you just want to make sure that people aren't looking at you and focusing in on your boner. Of course, things can get a little out of hand with this tip, especially if you start throwing your dinner plates across the restaurant. Plus, that will again, bring unwanted attention. Try pointing someone else out across the room so the attention is focused on them. "Look at this couple or "Look at that guy over there" are great starters for distracting whoever you're with.
Unfortunately, you can't control when your friend down below decides to pop up, but you can control how noticeable it is and who notices it. Perform all tips with precaution because the last thing that you want to do is attract more attention to yourself!